Abstract
Melt intercalation of montmorillonite (MMT) into polymeric matrices to improve the mechanical properties of polymers has evolved into a subject of tremendous fundamental and technological interest. The thermal treatment experienced during processing or end use can substantially affect the clay and diminish the target properties of polymer/clay nanocomposites (NCs) because of deintercalation or degradation of surface modifiers. In this work, changes in morphology, chemistry, and thermal stability of organically modified (OM) MMT after annealing in O2-rich and N2 environments are investigated. Degradation of the alkyl ammonium cation occurs at temperatures as low as 105 °C upon prolonged exposure in an O2-rich environment. X-ray diffractometry (XRD) performed in situ establishes the response of two OM-MMTs to elevated temperatures at short times, whereas ex situ XRD provides insight into high-temperature exposure at long times. Active sites on the silicate surfaces are found to induce scission of, as well as chemical interaction with, the chains comprising a polystyrene (PS) matrix. Size-exclusion chromatography indicates that PS chain scission occurs primarily after relatively short annealing times, whereas branching and cross-linking are more prevalent after long exposure times in an O2-rich environment.
Published Version
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